Formation of a Masking Layer on a Dielectric Region to Facilitate Formation of a Capping Layer on Electrically Conductive Regions Separated by the Dielectric Regions

ABSTRACT

A masking layer is formed on a dielectric region of an electronic device so that, during subsequent formation of a capping layer on electrically conductive regions of the electronic device that are separated by the dielectric region, the masking layer inhibits formation of capping layer material on or in the dielectric region. The capping layer can be formed selectively on the electrically conductive regions or non-selectively; in either case (particularly in the latter), capping layer material formed over the dielectric region can subsequently be removed, thus ensuring that capping layer material is formed only on the electrically conductive regions. Silane-based materials, such as silane-based SAMs, can be used to form the masking layer. The capping layer can be formed of an electrically conductive material (e.g., a cobalt alloy, a nickel alloy, tungsten, tantalum, tantalum nitride), a semiconductor material, or an electrically insulative material, and can be formed using any appropriate process, including conventional deposition processes such as electroless deposition, chemical vapor deposition, physical vapor deposition or atomic layer deposition.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to forming a capping layer on electricallyconductive regions of an electronic device to inhibit electromigrationin the electrically conductive regions (and, in some cases, enhanceinhibition of diffusion of material from the electrically conductiveregions). In particular, the invention relates to the formation of amasking layer on a dielectric region to facilitate formation of acapping layer on electrically conductive regions separated by thedielectric region.

2. Related Art

In the manufacture of various products, electrically conductive material(typically a metal, such as aluminum or copper) and dielectric material(often, a silicon dioxide-based material) are formed on, in, or as partof, a substrate such that regions of the electrically conductivematerial are separated by regions of dielectric material from otherregions of the electrical conductive material to define electricalelements (e.g., transistors, capacitors, resistors) and electricalinterconnections between electrical elements. (For convenience, asubstrate including—i.e., having as part of, or having formed on orin—electrically conductive regions separated by a dielectric region issometimes referred to herein as an Aelectronic device.@) Electroniccomponents (microprocessors, memory chips, etc.) for computers and otherdevices are well-known examples of such products. Other products too,such as flat panel displays, can also be constructed in that way.

During operation of an electronic device, the flow of current through anelectrical interconnection can cause electromigration (i.e., movement ofatoms of an electrically conductive material as a result of current flowthrough the electrically conductive material) which can result indeformation of the electrical interconnection (e.g., formation of voids,hillocks and/or extrusions), in particular at interface(s) with adjacentmaterial. Such deformation can result in undesirable current leakage orcurrent flow inhibition. As the characteristic dimension of electricalinterconnections of electronic devices becomes smaller (the manufactureof a variety of electronic devices now requires the cost-effectiveproduction of electrical interconnections having a characteristicdimension at the sub-100 nm size scale, and those required in futureelectronic devices will be increasingly smaller), the increased currentdensity flowing through those electrical interconnections renderselectromigration even more of a problem.

FIG. 1A is a simplified cross-sectional view of part of a semiconductordevice 100, illustrating electrically conductive regions 110 separatedby dielectric regions 120. (A semiconductor device is an electronicdevice in which the substrate is made of, in whole or in functionallysignificant part, a semiconductor material or materials.) Theelectrically conductive regions 110 and dielectric regions 120 areformed over (i.e., formed subsequent to, and through a common axis oraxes perpendicular to the layers of material formed in a device) anotherelectrically conductive region 105. The electrically conductive regions110 can be, for example, interconnections between the electricallyconductive region 105 and other electrically conductive material to besubsequently formed as part of the semiconductor device 100. In currentsemiconductor devices, copper is commonly used to form electricallyconductive regions and a silicon dioxide-based material (e.g., FSG,SiCOH, porous SiCOH, MSQ) is commonly used to form dielectric regions.Additionally, in current semiconductor devices, the dielectric regionoften includes a hard mask layer (which is often formed of asilicon-based—e.g., SiC_(x), SiN_(x), SiC_(x)N_(y)—material) formed atthe top (i.e., the surface of a region on which material can be formedduring subsequent processing of a device after formation of the region)of the dielectric region: in FIG. 1A—and FIG. 1B, discussed below—thesemiconductor device 100 is illustrated with a hard mask layer 120 aformed at the top of each of the dielectric regions 120.

FIG. 1B is a simplified cross-sectional view of the part of asemiconductor device 100, illustrating a dielectric barrier layer 130formed on the electrically conductive regions 110 and dielectric regions120. (In FIGS. 1A and 1B, a dielectric barrier layer 106 previouslyformed on the electrically conductive region 105 of the semiconductordevice 100 is also illustrated.) A Adielectric barrier layer@ is a layerof dielectric material in a semiconductor (or other electronic) devicethat is formed non-selectively on both electrically conductive regionsand dielectric regions that separate those electrically conductiveregions, after planarization of the top of the electrically conductiveregions and dielectric regions, to inhibit diffusion of material fromthe electrically conductive regions into adjacent regions (inparticular, into dielectric material subsequently formed over theelectrically conductive regions) of the semiconductor device. (Adielectric barrier layer is also sometimes referred to as a Avia etchstop layer,@ a Adielectric cap,@ or a Acapping layer.@ Herein, the termAdielectric barrier layer@ is used; as discussed in more detailelsewhere herein, Acapping layer@ is used to refer to a different typeof layer, which may, nevertheless, provide functionality associated witha dielectric barrier layer, such as inhibition of diffusion of materialfrom electrically conductive regions.) In current semiconductor devices,compositions including silicon together with carbon and/or nitrogen(i.e., SiC_(x), SiN_(x), SiC_(x)N_(y)) are commonly used to form adielectric barrier layer. Since these materials have a higher dielectricconstant than the dielectric materials that could otherwise be used(i.e., if it was not necessary or desirable to inhibit diffusion fromthe electrically conductive regions), an undesirable consequence of thepresence of a dielectric barrier layer is that the capacitanceassociated with the structure illustrated in FIG. 1B is increased, whichcan increase power consumption and/or decrease speed of operation of thesemiconductor device. Further, current common implementations of adielectric barrier layer do not adhere well to current commonimplementations of electrically conductive regions in semiconductordevices and, consequently, do little to inhibit electromigration in theelectrically conductive regions, which commonly is initiated at theinterface between the electrically conductive regions and the dielectricbarrier layer. In view of the foregoing, there is a need for improvedinhibition of electromigration in electrically conductive regions (and,in particular, at interface(s) of electrically conductive regions withadjacent regions formed of other material) of semiconductor (and otherelectronic) devices. There is also a need for reduction in capacitanceof the structure formed in the vicinity of the electrically conductiveregions of semiconductor (and other electronic) devices, whileadequately maintaining a barrier to diffusion of material from theelectrically conductive regions into adjacent regions formed of othermaterial. These needs have—and will continue to—become increasinglystrong as the characteristic dimension of features (e.g., electricalinterconnections) in electronic devices becomes smaller.

To inhibit electromigration at the interface between electricallyconductive regions and a dielectric barrier layer of a semiconductordevice, a layer of material has been selectively formed on theelectrically conductive regions before forming the dielectric barrierlayer. (ASelective@ formation of a material on a region or surface meansthat the material forms on that region or surface with better coverageof the region or surface than that with which the material forms onother region(s) or surface(s).) Such a selectively formed layer can bereferred to as, for example, a Acapping layer@ or a Aself-alignedbarrier layer;@ herein, the former term is generally used. Selectiveformation of a capping layer on electrically conductive regions isillustrated in FIGS. 2A through 2C. FIG. 2A is a simplifiedcross-sectional view of part of a semiconductor device 200, illustratingelectrically conductive regions 210 separated by a dielectric region220. FIG. 2B is a simplified cross-sectional view of the part of asemiconductor device 200, illustrating the selective formation of acapping layer 240 on the electrically conductive regions 210, but notthe dielectric region 220. FIG. 2C is a simplified cross-sectional viewof the part of a semiconductor device 200, illustrating a dielectricbarrier layer 230 formed on the capping layer 240 and the dielectricregion 220. Several ways of selectively forming the capping layer 240have been tried, using various materials and processes.

For example, a capping layer has been formed by selectively depositingan appropriate material on electrically conductive regions. A metallicmaterial is often used because metallic materials have the propertiesnecessary to catalyze growth of a layer on copper, which is commonlyused to form the electrically conductive regions. For instance,electroless deposition has been used to selectively deposit a metalalloy (e.g., an alloy of cobalt, tungsten and phosphorous; an alloy ofcobalt and boron; or an alloy of nickel, molybdenum and phosphorous) oncopper regions. An approach of this type is described in AHighReliability Cu Interconnection Utilizing a Low Contamination CoWPCapping Layer,@ by T. Ishigami et al., Proceedings of the 2004 IEEEInternational Interconnect Technology Conference, Jun. 7-9, 2004, pp.75-77, the disclosure of which is hereby incorporated by referenceherein. Or, for instance, chemical vapor deposition has been used toselectively deposit tungsten on copper regions. An approach of this typeis described in AA Robust, Deep-Submicron Copper Interconnect Structureusing Self-Aligned Metal Capping Method,@ by T. Saito et al.,Proceedings of the 2004 IEEE International Interconnect TechnologyConference, Jun. 7-9, 2004, pp. 36-38, the disclosure of which is herebyincorporated by reference herein. However, the selectivity of theseapproaches is inadequate to inhibit formation of capping layer material(which is electrically conductive) on dielectric region(s) (in FIGS. 2Band 2C, a thin layer of capping layer material—not designated by anumeral in FIGS. 2B and 2C—is shown on the dielectric region 220) to anextent that prevents unacceptable current leakage between electricallyconductive regions separated by those dielectric region(s) (this isparticularly so as the characteristic dimension of electricalinterconnections of electronic devices becomes smaller). This may bedue, at least in part, because residual material from the electricallyconductive regions that is left on the dielectric region(s) afterplanarization (e.g., chemical mechanical polishing) of the exposedsurfaces of the electrically conductive regions and dielectric region(s)provides nucleation sites for the capping layer material (which ischosen for its affinity for forming on the material of the electricallyconductive regions), significantly reducing preferential formation ofthe capping layer material on the electrically conductive regions ascompared to the dielectric region(s).

A capping layer has also been formed by chemically modifying a top partof each of the electrically conductive regions. For example, a cappinglayer has been formed by chemically modifying the top parts of copperregions using silicidation and nitridation (this can be accomplishedusing wet or dry processing). An approach of this type is described inAIntegration and performance of an alternative approach using coppersilicide as a self-aligned barrier for 45 nm technology node Cuinterconnects,@ by L. G. Gosset et al., Proceedings of the 2004 IEEEInternational Interconnect Technology Conference, Jun. 7-9, 2004, pp.15-17, the disclosure of which is hereby incorporated by referenceherein. However, the capping layer formed in this way undesirablyincreases resistance in the electrically conductive regions.

It has also been proposed to form a layer of organic material onelectrically conductive regions of a semiconductor device to inhibitelectromigration at the surfaces of the electrically conductive regions.(Such an organic layer can also be referred to as a Acapping layer.@)The use of organic material, which is a very poor electrical conductor,eliminates the potential for unacceptable current leakage betweenelectrically conductive regions resulting from the presence of thecapping layer, even if the process(es) and material(s) used to form theorganic layer are not particularly selective in preferentially formingthe organic layer on electrically conductive regions. U.S. PatentApplication Publication No. US 2004/0203192 describes such an approachin which a self-assembled organic monolayer (in particular, a thiolateself-assembled monolayer) is covalently bonded to metallic regions.However, it is believed that the thiolate self-assembled monolayersdescribed therein may not produce, when formed on copper (as discussedabove, a material commonly used to form electrically conductive regionsof a semiconductor device), a thermally stable capping layer thatremains continuous and defect-free (i.e., having sufficiently fewdefects according to one or more criteria) under operating conditions ofthe semiconductor device, and therefore may not adequately inhibitelectromigration, or provide an adequate copper diffusion barrier thatcan enable elimination of the dielectric barrier layer from thesemiconductor device.

SUMMARY OF THE INVENTION

According to the invention, a masking layer is formed on a dielectricregion of an electronic device so that during subsequent formation of acapping layer on electrically conductive regions of the electronicdevice that are separated by the dielectric region, the masking layerinhibits formation of the capping layer on or in the dielectric region.Prior to formation of the masking layer, exposed surfaces of theelectrically conductive regions and the exposed surface of thedielectric region can be processed in a specified manner (e.g., cleaned,functionalized). The masking layer can be formed selectively on thedielectric region so that no or negligible masking layer material isformed on the electrically conductive regions. Alternatively, themasking layer can be formed non-selectively on both the dielectricregions and the electrically conductive regions, and masking layermaterial formed on the electrically conductive regions subsequentlyremoved. The capping layer can be formed selectively on the electricallyconductive regions so that no or negligible capping layer material isformed on the masking layer. Alternatively, the capping layer can beformed non-selectively on both the electrically conductive regions andthe masking layer, and capping layer material formed on the maskinglayer subsequently removed (this can be done by removing only cappinglayer material from the masking layer, or by removing some or all of themasking layer and, with it, capping layer material formed thereon). (Ifnot already removed as part of removing capping layer material from overthe dielectric region, the masking layer can be removed from thedielectric region after formation of the capping layer.) In either case,capping layer material is inhibited from being formed on the maskinglayer over the dielectric region (in addition to the inhibition offormation of capping layer material on or in the dielectric region, dueto the presence of the masking layer on the dielectric region).Consequently, unlike previous approaches to forming a capping layer inwhich a layer of electrically conductive material (e.g., a cobalt alloy,a nickel alloy or tungsten) is selectively formed on electricallyconductive regions, the invention prevents the occurrence ofunacceptable current leakage between electrically conductive regionswhen electrically conductive material is used to form the capping layer.Since the invention inhibits formation of capping layer material over,on or in the dielectric region, the invention enables a great deal offlexibility in the selection of material(s) and/or process(es) forforming the capping layer, without regard for the selectivity of thecapping layer material for the electrically conductive regions vis-a-visthe dielectric region (and, in some embodiments, without regard for theselectivity of the capping layer material for any material). Forexample, the material(s) and/or process(es) used to form the cappinglayer can be chosen to enhance adhesion of the capping layer to theelectrically conductive regions (thus improving inhibition by thecapping layer of electromigration in the electrically conductiveregions). The material(s) and/or process(es) used to form the cappinglayer can also be chosen to produce a capping layer that does notunacceptably or undesirably increase resistance in the electricallyconductive regions: for example, the capping layer can be formed withoutreplacing any of the material of the electrically conductive regionswith capping layer material having a higher dielectric constant.Additionally or alternatively, the material(s) and/or process(es) usedto form the capping layer can be chosen to produce a capping layer thatis sufficiently effective in inhibiting diffusion of material used toform the electrically conductive regions that a dielectric barrier layercan be eliminated from the electronic device or, at least, reduced inthickness (with attendant decrease in capacitance and associatedbenefits). (In some embodiments of the invention, a conventionaldielectric barrier layer can be formed.) Further, since the maskinglayer inhibits formation of capping layer material in the dielectricregion, the invention facilitates the use of porous dielectric materialsthat are increasingly deemed desirable for use in electronic devices.Additionally, unlike the above-described approach in which a cappinglayer is produced by forming a thiolate self-assembled monolayer, theinvention enables production of a thermally stable capping layer oncopper (a material commonly used to form electrically conductive regionsof electronic devices) that remains continuous and defect-free undertypical operating conditions of many electronic devices.

The masking layer can be, for example, a molecularly self-assembledlayer, which can be formed as a monolayer (SAM) or a multilayer, and canbe formed of organic and/or inorganic material. The masking layer canalso be, for example, a layer formed from any class of materials knownto form with controlled film thickness, such as, for instance,multi-layer polyelectrolytes. The masking layer can also be, forexample, a layer formed on the surface of the dielectric region throughthe catalytic growth of inorganic or organic materials, such as polymerbrushes. The masking layer can also be, for example, a layer formed fromdendrimers, hyper-branched polymers, or block co-polymers. The maskinglayer can also be, for example, an ionic or electrochemically-enhancedself-assembled multilayer or monolayer. In particular, silane-basedmaterials can be used to form the masking layer in an embodiment of theinvention.

The capping layer can be formed of an electrically conductive material(e.g., a cobalt alloy, a nickel alloy, tungsten, tantalum, tantalumnitride), a semiconductor material, or an electrically insulativematerial. The capping layer can be formed using any appropriate process,including conventional deposition processes such as electrolessdeposition, chemical vapor deposition, physical vapor deposition(sputtering) or atomic layer deposition.

The invention can be implemented in, or used to process, a substratemade of any type of material. In particular, the invention canadvantageously be implemented in, or used to process, a semiconductorsubstrate, such as, for example, a silicon substrate,silicon-on-insulator substrate, silicon carbide substrate, strainedsilicon substrate, silicon germanium substrate or gallium arsenidesubstrate. The invention can be implemented in, or used to process, asubstrate including electrically conductive regions formed using anytype of electrically conductive material, such as copper or aluminum.The invention can be implemented in, or used to process, a substrateincluding a dielectric region made of any type of electricallyinsulative material, including non-porous and porous dielectricmaterials, and which may or may not include a hard mask layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a simplified cross-sectional view of part of a semiconductordevice, illustrating electrically conductive regions separated bydielectric regions.

FIG. 1B is a simplified cross-sectional view of the part of asemiconductor device of FIG. 1A, illustrating a dielectric barrier layerformed on the electrically conductive regions and dielectric regions.

FIG. 2A is a simplified cross-sectional view of part of a semiconductordevice, illustrating electrically conductive regions separated by adielectric region.

FIG. 2B is a simplified cross-sectional view of the part of asemiconductor device of FIG. 2A, illustrating the selective formation ofa capping layer on the exposed surfaces of the electrically conductiveregions, but not the exposed surface of the dielectric region.

FIG. 2C is a simplified cross-sectional view of the part of asemiconductor device of FIGS. 2A and 2B, illustrating a dielectricbarrier layer formed on the capping layer and the exposed surface of thedielectric region.

FIG. 3 is a flow chart of a method, according to an embodiment of theinvention, for producing a capping layer on electrically conductiveregions of an electronic device that are separated by a dielectricregion.

FIGS. 4A through 4E are a series of simplified cross-sectional views ofa part of an electronic device, illustrating stages in the production,in accordance with an embodiment of the invention, of a capping layer onelectrically conductive regions of the electronic device that areseparated by a dielectric region.

FIGS. 5A through 5D are a series of simplified cross-sectional views ofa part of an electronic device, illustrating stages in the production,in accordance with another embodiment of the invention, of a cappinglayer on electrically conductive regions of the electronic device thatare separated by a dielectric region.

FIGS. 6A through 6D are a series of simplified cross-sectional views ofa part of an electronic device, illustrating stages in the production,in accordance with another embodiment of the invention, of a cappinglayer on electrically conductive regions of the electronic device thatare separated by a dielectric region.

FIGS. 7A through 7C are a series of simplified cross-sectional views ofa part of an electronic device, illustrating stages in the production,in accordance with another embodiment of the invention, of a cappinglayer on electrically conductive regions of the electronic device thatare separated by a dielectric region.

FIGS. 8A through 8E are a series of simplified cross-sectional views ofa part of an electronic device, illustrating stages in the production,in accordance with another embodiment of the invention, of a cappinglayer on electrically conductive regions of the electronic device thatare separated by a dielectric region.

FIGS. 9A through 9D are a series of simplified cross-sectional views ofa part of an electronic device, illustrating stages in the production,in accordance with another embodiment of the invention, of a cappinglayer on electrically conductive regions of the electronic device thatare separated by a dielectric region.

FIGS. 10A through 10F are a series of simplified cross-sectional viewsof a part of an electronic device, illustrating stages in theproduction, in accordance with another embodiment of the invention, of acapping layer on electrically conductive regions of the electronicdevice that are separated by a dielectric region.

FIGS. 11A through 11E are a series of simplified cross-sectional viewsof a part of an electronic device, illustrating stages in theproduction, in accordance with another embodiment of the invention, of acapping layer on electrically conductive regions of the electronicdevice that are separated by a dielectric region.

FIGS. 12A through 12E are a series of simplified cross-sectional viewsof a part of an electronic device, illustrating stages in theproduction, in accordance with another embodiment of the invention, of acapping layer on electrically conductive regions of the electronicdevice that are separated by a dielectric region.

FIGS. 13A through 13D are a series of simplified cross-sectional viewsof a part of an electronic device, illustrating stages in theproduction, in accordance with another embodiment of the invention, of acapping layer on electrically conductive regions of the electronicdevice that are separated by a dielectric region.

FIG. 14A is a cross-sectional view of a structure including a dielectricregion on which is formed a masking layer. FIGS. 14B through 14D arecross-sectional views of the structure of FIG. 14A after furtherprocessing to modify the masking layer in a manner intended to producedesired characteristics of the masking layer, illustrating differentapproaches that can be used to modify the masking layer.

FIG. 15A is a cross-sectional view of a structure including a dielectricregion on which is formed a masking layer, a capping layer being formed,in turn, on the masking layer. FIGS. 15B through 15E are cross-sectionalviews of the structure of FIG. 15A after further processing to removethe capping layer, illustrating different approaches that can be used toeffect removal of the capping layer.

DETAILED DESCRIPTION OF THE INVENTION

According to the invention, on a substrate including (i.e., having aspart of, or having formed on or in) electrically conductive regionsseparated by a dielectric region (as indicated above, for convenience,such a substrate is sometimes referred to herein as an Aelectronicdevice@), a masking layer is formed on the dielectric region so that,during subsequent formation of a capping layer on the substrate, themasking layer inhibits formation of capping layer material on or in thedielectric region. (In practice, an electronic device will typicallyinclude many such electrically conductive regions and dielectricregions.) The electrically conductive regions can be electricalinterconnections between electrical elements (e.g., transistors,capacitors, resistors) of the electronic device, and it is anticipatedthat the invention will commonly be used in producing a capping layer onsuch electrical interconnections. The masking layer can be formedselectively on the dielectric region so that no or negligible maskinglayer material is formed on the electrically conductive regions.Alternatively, the masking layer can be formed non-selectively on boththe dielectric regions and the electrically conductive regions, andmasking layer material formed on the electrically conductive regionssubsequently removed. As used herein, a Acapping layer@ (also sometimesreferred to as a Aself-aligned barrier layer@) is a layer of materialformed on electrically conductive regions of an electronic device,typically after planarization of the top of the electrically conductiveregions, to inhibit electromigration in the electrically conductiveregions and, in particular, to inhibit electromigration in theelectrically conductive regions better than a dielectric barrier layer(discussed above) that would otherwise be formed on the electricallyconductive regions. (Additionally, in some cases, as discussed in moredetail below, a capping layer may inhibit diffusion of material from theelectrically conductive regions and, in particular, may inhibit suchdiffusion to an extent that enables elimination, or reduction of thethickness, of a dielectric barrier layer that would otherwise be formedon the capping layer.) The capping layer can be formed selectively onthe electrically conductive regions so that no or negligible cappinglayer material is formed on the masking layer: in particular, thematerial(s) and/or process(es) used to form the masking layer and/or thecapping layer can be tailored to inhibit formation of capping layermaterial on the masking layer, thus fostering the selective formation ofthe capping layer on the electrically conductive regions. Alternatively,the capping layer can be formed non-selectively on both the electricallyconductive regions and the masking layer, and capping layer materialformed on the masking layer subsequently removed (this can be done, forexample, by removing some or all of the masking layer and, with it,capping layer material formed thereon). (The foregoing alternativesencompass forming the masking layer or capping layer with any degree ofselectivity. As indicated above, Aselective@ formation of a material ona region or surface means that the material forms on that region orsurface with better coverage of the region or surface than that withwhich the material forms on other region(s) or surface(s). In anyembodiment of the invention, masking layer material formed onelectrically conductive regions or capping layer material formed on themasking layer can be removed if deemed necessary or desirable. However,as discussed further below, removal of masking layer material formed onelectrically conductive regions or capping layer material formed on themasking layer may not be necessary in some cases, e.g., when negligibleamounts of masking layer material are formed on electrically conductiveregions or negligible amounts of capping layer material are formed onthe masking layer, such as may be the case when the masking layer orcapping layer, respectively, is formed selectively on the electricallyconductive regions.) In either case, capping layer material is inhibitedfrom being formed on the masking layer over the dielectric region (inaddition to the inhibition of formation of capping layer material on orin the dielectric region, due to the presence of the masking layer onthe dielectric region). Consequently, unlike previous approaches toforming a capping layer in which a layer of electrically conductivematerial (e.g., a cobalt alloy, nickel alloy or tungsten) is selectivelydeposited on electrically conductive regions, the invention prevents theoccurrence of unacceptable current leakage between electricallyconductive regions when electrically conductive material is used to formthe capping layer. Since the invention inhibits formation of cappinglayer material over, on or in the dielectric region, the inventionenables a great deal of flexibility in the selection of material(s)and/or process(es) for forming the capping layer, without regard for theselectivity of the capping layer material for the electricallyconductive regions vis-a-vis the dielectric region (and, in someembodiments, without regard for the selectivity of the capping layermaterial for any material): this can enable, for example, the use ofmaterial(s) and/or process(es) in formation of the capping layer thatwould otherwise not form the capping layer with sufficient selectivity,such as those described above in the Background section. For example,the material(s) and/or process(es) used to form the capping layer can bechosen to enhance adhesion of the capping layer to the electricallyconductive regions (thus improving inhibition by the capping layer ofelectromigration in the electrically conductive regions). Thematerial(s) and/or process(es) used to form the capping layer can alsobe chosen to produce a capping layer that does not unacceptably orundesirably increase resistance in the electrically conductive regions;for example, the capping layer can be formed without replacing any ofthe material of the electrically conductive regions with capping layermaterial having a higher dielectric constant. Additionally oralternatively, the material(s) and/or process(es) used to form thecapping layer can be chosen to produce a capping layer that issufficiently effective in inhibiting diffusion of material used to formthe electrically conductive regions (e.g., copper) that a dielectricbarrier layer can be eliminated from the electronic device or, at least,reduced in thickness (with attendant decrease in capacitance andassociated benefits). Further, since the masking layer inhibitsformation of capping layer material in the dielectric region, theinvention facilitates the use of porous dielectric materials that areincreasingly deemed desirable for use in electronic devices.Additionally, unlike the above-described approach in which a cappinglayer is produced by forming a thiolate self-assembled monolayer, theinvention enables production of a thermally stable capping layer (e.g.,using any of the above-described processes for selectively forming acapping layer by selectively depositing a metallic material) on copper(a material commonly used to form electrically conductive regions ofsemiconductor devices, as well as other electronic devices) that remainscontinuous and defect-free (i.e., having sufficiently few defectsaccording to one or more criteria) under typical operating conditions ofmany electronic devices (e.g., for semiconductor devices, this meansthat the capping layer should be able to withstand temperatures up toabout 450ΕC).

The invention can be used in the processing of a substrate made of anytype(s) of material. This is particularly so since, as described in moredetail below, the invention can be implemented so that substratematerial (e.g., a dielectric region) is functionalized to have desiredproperties, such as desired adhesion. (As used herein, and as known tothose skilled in the chemical arts, Afunctionalization@ of a materialrefers to modifying the characteristics of an exposed part of thematerial to achieve a desired interaction with another materialsubsequently formed on the exposed part of the material.) In particular,the invention can advantageously be used in the processing of asemiconductor substrate as is commonly done in the manufacture ofcomponents for use in the electronics industry. The invention can alsobe used in the processing of a substrate for use in the production of aflat panel display, which substrates are now commonly made of silicon.The invention can be used in the processing of any type of semiconductorsubstrate, such as, for example, a silicon substrate,silicon-on-insulator substrate, silicon carbide substrate, strainedsilicon substrate, silicon germanium substrate or gallium arsenidesubstrate.

Further, the invention can be used in the processing of a substrate ofany shape or size. For example, the invention can be used in theprocessing of semiconductor substrates used in the production ofelectronic components, which substrates are typically circular, as wellas in the processing of substrates used in the production of flat paneldisplays, which substrates are typically rectangular. The invention canbe used in the processing of small semiconductor substrates having areasof less than 1 in.² up to the 12 inch (300 mm) semiconductor substratescurrently used in the production of many electronic components; ingeneral, there is no limit to the size of substrate that can beprocessed, so that the invention can be used to process each succeedinglarger generation of semiconductor substrates used to produce electroniccomponents. The invention can also be used to process the relativelylarge substrates that are used in the production of flat panel displays(now, commonly rectangular substrates on the order of about 1 m², but,in some cases, larger, and expected to increase in size in the future).The invention can also be scaled for use in roll-to-roll processingapplications for flexible substrates having a fixed width, but(theoretically) unlimited length (a manner of substrate processing thatcan be particularly useful in the production of flat panel displays);for example, such substrate rolls can be hundreds of feet long.

The invention can be used in processing electronic devices includingelectrically conductive regions and dielectric regions of any type ofmaterial. This is particularly so since the masking layer (and, in somecases, the electrically conductive regions and dielectric regions) canbe functionalized to have desired properties, such as desired adhesionand/or diffusion barrier properties. In semiconductor devices used inthe production of electronic components, for example, the electricallyconductive regions are often made of copper or aluminum; the inventioncan readily be used in processing such substrates. A variety ofdielectric materials (e.g., SiCOH dielectric materials, including porousSiCOH dielectric materials) are used to form dielectric regions ofsemiconductor devices used in the production of electronic componentsand the invention is compatible for use with all. In many semiconductordevices, a hard mask layer (which is often formed of asilicon-based—e.g., SiC_(x), SiN_(x), SiC_(x)N_(y)—material) is formedon top of a dielectric material of which the dielectric region isprimarily composed; the invention can also readily be used in theproduction of an electronic device using such substrates.

Increasingly, it is becoming desirable to use porous dielectricmaterials in electronic devices (which may or may not have a hard masklayer formed thereon), particularly semiconductor devices used in theproduction of electronic components. A porous material—in this context,a porous dielectric material—is particularly susceptible to diffusion ofother material therein. For example, a dielectric region made of aporous dielectric material is particularly susceptible to diffusiontherein of capping layer material; especially when the capping layermaterial is a metallic material, as is often the case (as discussedabove), diffusion of capping layer material into a dielectric regionincreases the likelihood of unacceptable current leakage. Additionally,as described above, residual material from electrically conductiveregions that is left on a dielectric region after planarization (e.g.,chemical mechanical polishing) of the exposed surfaces of theelectrically conductive regions and dielectric region can providenucleation sites for the capping layer material, thus significantlyreducing preferential formation of the capping layer material on theelectrically conductive regions during formation of a capping layer. Adielectric region made of a porous dielectric material is particularlysusceptible to diffusion therein of such residual material, thusexacerbating this problem. Thus, use of the invention in processingsubstrates including dielectric regions made of porous dielectricmaterial is particularly advantageous because the masking layer inhibitsdiffusion of material into the porous dielectric material.

FIG. 3 is a flow chart of a method 300, according to an embodiment ofthe invention, for producing a capping layer on electrically conductiveregions of an electronic device that are separated by a dielectricregion. In steps 301 and 302 of the method 300, a masking layer isformed on the electronic device so that the masking layer is formed onthe dielectric region, but not the electrically conductive regions. Insteps 303 through 306 of the method 300, after formation of the maskinglayer, a capping layer is formed on the electronic device so that thecapping layer is formed on the electrically conductive regions, but noton or in the dielectric region or the masking layer. The presence of themasking layer inhibits formation of capping layer material on or in thedielectric region that may otherwise have occurred if the masking layerwas not present, with attendant benefits as described in more detailelsewhere herein. Further, steps of the method 300 can be implemented inany of several ways, discussed in more detail below, to inhibitformation of capping layer material on or in the masking layer.Consequently, the method 300 produces a capping layer so that cappinglayer material is formed only on the electrically conductive regions (noor negligible capping layer material is formed over, on or in adielectric region separating electrically conductive regions),eliminating unacceptable current leakage between electrically conductiveregions that has been a problem with previous approaches to depositing ametallic capping layer that have not achieved sufficient selectivity informing capping layer material on the electrically conductive regions inpreference for a dielectric regions separating the electricallyconductive regions. In step 307 of the method 300, a dielectric barrierlayer can be formed on the electronic device or not, depending on theproperties of the capping layer, as discussed further below. Particularways of implementing, modifications to, and other aspects of, the method300 are described in more detail below.

FIGS. 4A through 4E, 5A through 5D, 6A through 6D, 7A through 7C, 8Athrough 8E, 9A through 9D, 10A through 10F, 11A through 11E, 12A through12E, and 13A through 13D are each sets of simplified cross-sectionalviews of a part of an electronic device, illustrating the production, inaccordance with various embodiments of the invention, of a capping layer440 over electrically conductive regions 410 of the electronic devicethat are separated by a dielectric region 420. The electricallyconductive regions 410 can be interconnections between electricalelements of the electronic device, such as, for example, transistors,capacitors and resistors. The dielectric region 420 is illustrated witha hard mask layer 420 a formed as a top part of the dielectric region420, as is commonly the case in current electronic devices; however, thedielectric region 420 need not necessarily include the hard mask layer420 a. As discussed further below, the method 300 can be used inproducing a capping layer in accordance with each of the embodiments ofthe invention illustrated by those sets of simplified cross-sectionalviews of a part of an electronic device. However, the method 300 canalso produce a capping layer in accordance with embodiments of theinvention that are different from those illustrated in FIGS. 4A through4E, 5A through 5D, 6A through 6D, 7A through 7C, 8A through 8E, 9Athrough 9D, 10A through 10F, 11A through 11E, 12A through 12E, and 13Athrough 13D. In particular, in the embodiments of the inventionillustrated in FIGS. 4A through 4E, 5A through 5D, 6A through 6D, 7Athrough 7C, 8A through 8E, 9A through 9D, 10A through 10F, 11A through11E, 12A through 12E, and 13A through 13D, due to imperfect selectivityor non-selectivity of the formation of the masking layer 450, maskinglayer material can be formed on the electrically conductive regions 410(as illustrated in FIGS. 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A and 13A)that is subsequently removed (as illustrated in FIGS. 4B, 5B, 6B, 7B,8B, 9B, 10B, 11B, 12B and 13B) prior to forming the capping layer 440.However, the formation of the masking layer 450 may also be accomplishedwith greater selectivity so that no masking layer material is formed onthe electrically conductive regions 410 (in that case, the intermediatestructure illustrated in FIGS. 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A and13A would not occur) or so that a negligible amount of masking layermaterial is formed on the electrically conductive regions 410 that neednot necessarily be removed from the electrically conductive regions 410(in that case, the intermediate structure illustrated in FIGS. 4B, 5B,6B, 7B, 8B, 9B, 10B, 11B, 12B and 13B would not occur and thesubsequently formed structures illustrated in further figures of eachset of simplified cross-sectional views of a part of an electronicdevice would include the negligible amount of masking layer materialformed on the electrically conductive regions 410).

Prior to forming a masking layer in accordance with the invention, theexposed surfaces of the electrically conductive regions and the exposedsurface of the dielectric region are prepared for processing inaccordance with the invention. This surface preparation entails at leastone or more cleaning steps (e.g., a deionized water rinse and/or any ofa variety of other well-known surface cleaning step(s)) to removecontaminants left from previous processing. (Such cleaning may removesome, but typically would not remove all, residual electricallyconductive material left on a dielectric region after planarization ofthe exposed surfaces of the electrically conductive regions anddielectric region, and does not, therefore, negate the efficacy of theinvention in preventing such residual electrically conductive materialfrom promoting undesired nucleation of capping layer material on thedielectric region, as discussed elsewhere herein.) The surfacepreparation can include other processing steps as well. For example, theexposed surfaces of the electrically conductive regions and/or theexposed surface of the dielectric region can be functionalized tofacilitate selective formation of the masking layer: in particular, thesurface of the dielectric region can be functionalized to promoteformation of the masking layer and the exposed surfaces of theelectrically conductive regions can be functionalized to inhibitformation of the masking layer. Similarly, the exposed surfaces of theelectrically conductive regions and/or the exposed surface of thedielectric region can also be functionalized to facilitate selectiveformation of the capping layer: in particular, the surface of thedielectric region can be functionalized to inhibit formation of thecapping layer (though the use of a masking layer in accordance with theinvention may render this unnecessary or, at least, of greatly reducedimportance) and the exposed surfaces of the electrically conductiveregions can be functionalized to promote adhesion of the capping layer.In general, the particular manner in which the surfaces of theelectrically conductive regions and/or the surface of the dielectricregion are functionalized depends on the nature of the materials used toform the electrically conductive regions, the dielectric region and themasking layer, and the desired propert(ies) (e.g., passivation,promotion of material formation) to be produced. For example, adielectric region formed of a silicon dioxide-based dielectric materialcan be functionalized to produce a large number of hydroxyl groups atthe surface of the dielectric region, to which a self-assembledmonolayer (which can embody the masking layer) has an affinity forattachment, thus promoting formation of the masking layer on thedielectric region. Additionally, a molecule used to form a molecularlyself-assembled layer can be established to include a head group thatcovalently bonds with an exposed hydroxyl group of the material used toform a dielectric region. Though not shown in FIG. 3, such surfacepreparation can be included as additional step(s) in the method 300 inaccordance with particular embodiment(s) of the invention.

As indicated above, in steps 301 and 302 of the method 300, a maskinglayer is formed on an electronic device so that the masking layer isformed on a dielectric region of the electronic device, but not on theelectrically conductive regions of the electronic device that areseparated by the dielectric region. (Formation of a masking layer on adielectric region encompasses negligible failure of the masking layermaterial to cover the dielectric region, i.e., masking layer materialcoverage failure that does not impair performance of a method accordingto the invention or the functionality of an electronic device in theproduction of which a method according to the invention is used.Additionally, no formation of a masking layer on electrically conductiveregions encompasses negligible formation of masking layer material onthe electrically conductive regions, i.e., masking layer materialcoverage that does not impair performance of a method according to theinvention or the functionality of an electronic device in the productionof which a method according to the invention is used.) As indicated bystep 301, the masking layer can be formed selectively on the dielectricregion or the masking layer can be formed non-selectively on both thedielectric region and the electrically conductive regions. (Selectiveformation of a masking layer on a dielectric region encompassesnegligible formation of masking layer material on the electricallyconductive regions, i.e., masking layer material coverage that does notimpair performance of a method according to the invention or thefunctionality of an electronic device in the production of which amethod according to the invention is used. Non-selective formation of amasking layer on both the dielectric region and the electricallyconductive regions encompasses formation of the masking layer with nopreference for the dielectric region or electrically conductive regions,with some degree of preference for the electrically conductive regions,or with preference for the dielectric region that is inadequate toresult in the formation of no or negligible masking layer material onthe electrically conductive regions, i.e., in the last case, withpreference that is inadequate to constitute selective formation of themasking layer on the dielectric region.) When the masking layer isformed non-selectively on both the dielectric region and theelectrically conductive regions, all masking layer material formed onthe electrically conductive regions is subsequently removed, asindicated by step 302. (Removal of all masking layer material formed onthe electrically conductive regions encompasses leaving negligiblemasking layer material formed on the electrically conductive regions,i.e., masking layer material coverage that does not impair performanceof a method according to the invention or the functionality of anelectronic device in the production of which a method according to theinvention is used.) Each of FIGS. 4A and 4B, 5A and 5B, 6A and 6B, 7Aand 7B, 8A and 8B, 9A and 9B, 10A and 10B, 11A and 11B, 12A and 12B, and13A and 13B illustrate non-selective formation of a masking layer 450 onboth the dielectric region 420 and the electrically conductive regions410, followed by removal of all masking layer material formed on theelectrically conductive regions 410, leaving the masking layer 450formed only on the dielectric region 420.

In general, the masking layer can be formed using any material(s) andprocess(es) that produce a masking layer that achieves desired functionsof the masking layer, e.g., selective formation on a dielectric region,provision of a good barrier to diffusion of capping layer material. Themasking layer can be formed using either wet processing (e.g., immersionof a substrate in a chemical bath, spraying or spinning of chemicalfluid on to a substrate) or dry processing (e.g., vapor deposition). Ifwet processing is used, typically a rinsing process is used afterwardsto clean the electronic device, which is then followed by a dryingprocess. Additionally, if wet processing is used, vibration of specifiedamplitude and/or frequency (e.g., high frequency vibration, such asultrasonic or megasonic vibration) can be imparted to the electronicdevice during the processing to facilitate (e.g., speed up) theprocessing. The masking layer can be deposited or grown on thedielectric region. The masking layer can also be formed by stamping. Itis anticipated that it will often be desirable to form the masking layerof an electrically insulative (effectively non-conductive) material,since the masking layer is formed in regions that, in the finishedelectronic device, must be electrically non-conductive. However, inembodiments of the invention in which the masking layer is completelyremoved from the electronic device (see, e.g., FIGS. 4D, 5D, 8D, 9D, 10Eand 11E), the masking layer can be formed of an electrically conductiveor semiconductor material. The use of such materials may be desirable,notwithstanding the potential problems that may result from theirelectrical conductivity, if the use of such materials provides otherbeneficial properties of a masking layer, e.g., selective formation ofthe masking layer on the dielectric region, good barrier to diffusion ofthe capping layer material. After formation of the masking layer, themasking layer can be functionalized or otherwise modified (e.g.,chemically, thermally and/or photo-chemically modified) in a desiredmanner to produce desired properties (e.g., to produce a desiredpropensity for formation on the masking layer of material tosubsequently be formed on the electronic device, such as a capping layeror a dielectric barrier layer, or to enable some or all of the maskinglayer to be removed after formation of the capping layer so that cappinglayer material formed on the masking layer can be removed).

The masking layer can be, for example, a molecularly self-assembledlayer, which can be formed as a monolayer (SAM) or a multilayer, and canbe formed of organic and/or inorganic material. A molecularlyself-assembled layer can be produced by forming (e.g., depositing orgrowing) additional material on the surface of the dielectric region, orby chemically activating or modifying the material of the dielectricregion to produce a new distinct layer of material. The ability totailor the molecule type, head group, terminal group and/or chain lengthof a molecularly self-assembled layer advantageously providesflexibility in establishing the characteristics of a masking layer,which can be used to produce desired masking layer properties, asdiscussed elsewhere herein. The masking layer can also be, for example,a layer formed from any class of materials known to form with controlledfilm thickness, such as, for instance, multi-layer polyelectrolytes. Themasking layer can also be, for example, a layer formed on the surface ofthe dielectric region through the catalytic growth of inorganic ororganic materials. One example of this approach is the growth of polymerbrushes from surface-initiated polymerization reactions. The surfaceinitiators can be present in the material of the dielectric region orattached to the surface of the dielectric region through chemical orphysioadsorptive means. The masking layer can also be, for example, alayer formed from dendrimers, hyper-branched polymers, or blockco-polymers. The masking layer can also be, for example, an ionic orelectrochemically-enhanced self-assembled multilayer or monolayer.

Silane-based materials can be used to form a masking layer inembodiments of the invention. For example, some silane-based SAMsadvantageously have relatively high breakdown temperatures, which may bedesirable if the masking layer is not removed by subsequent processingof the electronic device, so that the masking layer will not experiencefailure during operation of the electronic device that produces hightemperatures in the electronic device. Additionally, as discussed inmore detail below, some silane-based SAMs adhere well to (form strongcovalent bonds with) silicon-based dielectric materials (of which thedielectric region is commonly formed) and do not adhere well to metallicmaterials such as copper (of which the electrically conductive regionsare commonly formed), which can make them desirable for use in someapplications of the invention because they facilitate the selectiveformation of the masking layer. Further, as also discussed in moredetail below, silane-based SAMs can be tailored to facilitate removal ofthe SAM from a dielectric region, which can be useful in embodiments ofthe invention in which the masking layer is removed from the dielectricregion. Additionally, as also discussed in more detail below,silane-based SAMs can be tailored to promote or inhibit the formation ofparticular material thereon, which can be useful in inhibiting formationof capping layer material on a masking layer and/or promoting adhesionof a dielectric barrier layer formed on a masking layer.

The characteristics of a masking layer formed in an embodiment of theinvention can be established to produce desired properties of themasking layer. For example, the type of molecule(s) used to form amolecularly self-assembled layer can be chosen, and the characteristicsof the molecule, such as the head group, terminal group and/or length(e.g., the number of carbon atoms in the organic backbone of amolecule), can be established, to produce desired properties of themolecularly self-assembled layer. The particular manner in which thecharacteristics of a masking layer are tailored (in turn, thematerial(s) and/or process(es) used to form the masking layer) can—and,it is anticipated, typically will—depend on the particular applicationof the invention, e.g., the properties of the dielectric region(including, in particular, the adhesion properties of the dielectricregion), the necessity or desirability of avoiding formation of maskinglayer material on the electrically conductive regions (which can makeimportant the adhesion properties of the electrically conductiveregions), the characteristics of the material(s) and/or process(es) usedto form the capping layer (in particular, the propensity of the cappinglayer material for formation on, and/or diffusion into, the maskinglayer), and/or the characteristics of the material(s) (e.g., dielectricbarrier layer, such as a silicon carbide layer or a silicon nitridelayer) and/or process(es) used to subsequently form material on themasking layer.

For example, the material(s) and/or process(es) used to form the maskinglayer can be established to facilitate achievement of one or more of thefollowing possibly desirable properties of a masking layer produced by amethod, or part of a structure, in accordance with an embodiment of theinvention. It can be desirable to use material(s) and/or process(es)that produce a masking layer with high selectivity for the dielectricregion (i.e., that form better on the dielectric region than on theelectrically conductive regions). In some electronic devices, a SiCOHdielectric material is used; consequently, in some embodiments of theinvention, it can be desirable that the invention be implemented usingmaterial(s) and/or process(es) that can be used to form a masking layerwith high selectivity for a SiCOH dielectric material. Or, in someelectronic devices, a silicon-based hard mask layer is formed on top ofa dielectric material of which the dielectric region is primarilycomposed; consequently, in some embodiments of the invention, it can bedesirable that the invention be implemented using material(s) and/orprocess(es) that can be used to form a masking layer with highselectivity for a silicon-based hard mask layer. It can be desirable touse material(s) and/or process(es) that produce a masking layer that canadhere well to a dielectric barrier layer (commonly formed of acomposition including silicon together with carbon and/or nitrogen,i.e., SiC_(x), SiN_(x), SiC_(x)N_(y)) or other material to besubsequently formed on the masking layer. It can be desirable to usematerial(s) and/or process(es) that produce a masking layer thatprovides a good barrier to diffusion of the capping layer material(e.g., a cobalt alloy, such as a cobalt-tungsten-phosphorous alloy),both during production of the capping layer and during operation of thefinished electronic device (if the masking layer is left as part of thefinished electronic device). It can be desirable to use material(s)and/or process(es) that produce a masking layer that facilitates removalof some or all of the masking layer (and, with it, any capping layermaterial that may have been formed thereon), e.g., that produce aterminal group of a molecularly self-assembled layer that can be cleavedfrom the rest of the molecularly self-assembled layer or that produce anorganic backbone of a molecularly self-assembled layer that can bebroken down and removed. It can be desirable to use material(s) and/orprocess(es) that can produce a masking layer that is continuous anddefect-free and that, if to be left as part of the electronic device,remains so even when subjected to the thermal and chemical environmentassociated with further processing to produce the electronic deviceand/or operation of the finished electronic device. For semiconductordevices, this means, for example, that the masking layer should be ableto withstand temperatures up to about 450ΕC. This also means, forexample, that the masking layer should be chemically compatible with thematerials and processes used to produce the capping layer and (ifpresent) the dielectric barrier layer. It can also be desirable to usematerial(s) and/or process(es) that enable rapid (e.g., less than about60 seconds) production of a masking layer. Ways of implementing theinvention to produce such properties of a masking layer are described inmore detail elsewhere herein.

The characteristics of the masking layer can be established (i.e.,appropriate material(s) and/or process(es) used) to produce desiredmaterial formation properties with respect to the dielectric region andthe electrically conductive regions. For example, the characteristics ofthe masking layer can be established so that the masking layer formsselectively on the dielectric region in preference for formation on theelectrically conductive regions. (However, as discussed elsewhereherein, the invention can also be implemented so that the formation ofthe masking layer is not selective; in that case, masking layer materialformed on electrically conductive regions can be removed in a subsequentprocessing step, as described further below.) In this regard, theinvention can take advantage of the fact that, for some materials usedto form electrically conductive regions on an electronic device (e.g.,copper), few materials adhere well to the electrically conductiveregions, providing greater flexibility in selecting material(s) and/orprocess(es) for selectively forming the masking layer. Thecharacteristics of the masking layer can also, additionally oralternatively, be established to facilitate removal of the masking layerfrom the dielectric region after formation of the capping layer.

For example, the molecule used to form a molecularly self-assembledmasking layer can be specified to include a head group that is morelikely to adhere to the dielectric region than to the electricallyconductive regions. For instance, a molecule used to form a molecularlyself-assembled layer can be specified to include a head group thatcovalently bonds with an exposed hydroxyl group of the dielectricregion. As discussed above, some silane-based SAMs adhere well tosilicon-based dielectric materials commonly used to form a dielectricregion and do not adhere well to metallic materials such as copper thatare commonly used to form electrically conductive regions, thus makingthem appropriate for use in embodiments of the invention in which themasking layer is selectively formed on the dielectric region. Forexample, it is known that a silane with one or more hydrolysablesubstituents of the general formula R_(n)SiX_(4−n) (where R can be, forexample, alkyl, substituted alkyl, aryl or substituted aryl, and X canbe, for example, halo, alkoxy, aryloxy or amino) can form a SAM that canexhibit strong covalent or non-covalent attachment to particularsurfaces. Typically, SAM surface attachment is enhanced on a surfacehaving a relatively high density of acidic functionalities such ashydroxyl or hydroxysilyl groups. Silicon-based material surfaces such asSiO₂, SiOH and SiOC surfaces possess relatively high densities ofhydroxyl groups. Thus, a silane-based SAM can be expected to form withgreater adhesion to a surface of a silicon-based material (of which adielectric region is commonly formed) than to a surface of a metallicmaterial (of which electrically conductive regions are commonly formed).

A silane-based SAM can also be tailored to reversibly adhere to asurface depending on the nature and substitution of a silane precursormaterial. For example, silicon-based SAM precursors with a singlehydrolysable substituent (e.g., of the general formula R¹R²R³SiX) areknown to produce a SAM that can be formed on, and reversibly detachedfrom, a functionalized surface (e.g., a surface having a relatively highdensity of acidic functionalities) under specific reaction conditions.For instance, a SAM can be formed on a substrate through reaction in anorganic solvent medium (e.g., toluene, hexane, dichloromethane ormixtures thereof). Such a SAM can be made to be stable to aqueoussolvent media over a range of pH conditions. This would allow, forexample, subsequent electroless deposition of capping layer materialwhile maintaining the integrity of the SAM. Removal of the SAM can thenbe accomplished through treatment with an aqueous or mixedorganic/aqueous solution at elevated pH (e.g. NaOH/MeOH/H₂O at pH 12).Thus, the adhesion properties of a silane-based SAM can be controlled tofacilitate attachment to a dielectric region, then removal from thedielectric region after formation of the capping layer. Silanization ofsurfaces is discussed in detail in, for example, Silanes, Surfaces andInterfaces (Chemically Modified Surfaces, Vol. 1), edited by Donald E.Leyden, Gordon & Breach Science Publishers, 1986, the disclosure ofwhich is hereby incorporated by reference herein; principles discussedtherein can be used in implementing aspects of the invention, as can beappreciated in view of the description elsewhere herein of the use ofsilane-based materials in implementing aspects of the invention.

The characteristics of the masking layer can also be established (i.e.,appropriate material(s) and/or process(es) used) to produce desiredmaterial formation and/or adhesion properties with respect to materialto be formed on the electronic device subsequent to formation of themasking layer. In particular, the characteristics of the masking layercan be established so that capping layer material does not form well onthe masking layer, thus facilitating selective formation of the cappinglayer on the electrically conductive regions. (However, as discussedelsewhere herein, the invention can also be implemented so that theformation of the capping layer is not selective; in that case, cappinglayer material formed on the masking layer can be removed in asubsequent processing step, as described further below, and thedesirability of establishing the characteristics of the masking layer toinhibit formation of capping layer material on the masking layer isgenerally diminished.) The characteristics of the masking layer can alsobe established so that dielectric barrier layer material (if adielectric barrier layer is to be formed) adheres well to the maskinglayer.

FIG. 14A is a cross-sectional view of a structure 1400 including adielectric region 1401 on which is formed a masking layer 1402. Themasking layer 1402 is a self-assembled monolayer (SAM). The SAMincludes: 1) a head group 1402 a formed on the dielectric region 1401,2) a linking group 1402 b connected to the head group 1402 a, and 3) aterminal group 1402 c, connected to the linking group 1402 b, on whichmaterial can subsequently be formed. Without modification, the maskinglayer 1402 has characteristic(s), with respect to formation of materialon the electronic device subsequent to formation of the masking layer,in accordance with the nature of the terminal group 1402 c used in themasking layer 1402. FIGS. 14B through 14D are cross-sectional views ofthe structure 1400 after further processing to modify the masking layer1402 in a manner intended to produce desired characteristics of themasking layer with respect to formation of material on the electronicdevice subsequent to formation of the masking layer (and, in particular,one or more characteristics that are different from those provided bythe unmodified terminal group 1402 c of the masking layer 1402), asdiscussed above. Each of FIGS. 14B through 14D illustrates a differentgeneral type of approach that can be used to modify the masking layer1402. In FIG. 14B, the head group 1402 a of the masking layer 1402 iscleaved, removing part of the head group 1402 a, all of the linkinggroup 1402 b and all of the terminal group 1402 c of the masking layer1402; the part of the head group 1402 a remaining on the dielectricregion 1401 (designated as H= in FIG. 14B to indicate thatcharacteristic(s) are provided that are different from those provided bythe unmodified head group 1402 a of FIG. 14A) provides the desiredcharacteristic(s) for the masking layer 1402. In FIG. 14C, the linkinggroup 1402 b of the masking layer 1402 is cleaved, removing part of thelinking group 1402 b and all of the terminal group 1402 c of the maskinglayer 1402; the part of the linking group 1402 b remaining on thedielectric region 1401 (designated as L= in FIG. 14C to indicate thatcharacteristic(s) are provided that are different from those provided bythe unmodified linking group 1402 b of FIG. 14A) provides the desiredcharacteristic(s) for the masking layer 1402. In FIG. 14D, the terminalgroup 1402 c of the masking layer 1402 is cleaved, removing part of theterminal group 1402 c of the masking layer 1402; the part of theterminal group 1402 c remaining on the dielectric region 1401(designated as T= in FIG. 14D to indicate that characteristic(s) areprovided that are different from those provided by the unmodifiedterminal group 1402 c of FIG. 14A) provides the desiredcharacteristic(s) for the masking layer 1402.

There are other general types of approaches, not illustrated in FIGS.14B through 14D, that can be used to modify a masking layer. Forexample, in the structure 1400, the bond between the head group 1402 aand the linking group 1402 b could be broken, resulting in the removalof the linking group 1402 b and the terminal group 1402 c of the maskinglayer 1402; the head group 1402 a remaining on the dielectric region1401 provides the desired characteristic(s) for the masking layer 1402.Or, the bond between the linking group 1402 b and the terminal group1402 c could be broken, resulting in the removal of the terminal group1402 c of the masking layer 1402; the linking group 1402 b remaining onthe dielectric region 1401 provides the desired characteristic(s) forthe masking layer 1402. Or, the terminal group 1402 c could befunctionalized (rather than cleaved); the modified terminal group 1402 cprovides the desired characteristic(s) for the masking layer 1402. (Infact, in each of the other general types of approaches describedabove—i.e., cleaving the head group 1402 a, linking group 1402 b orterminal group 1402 c, or breaking the bond between the head group 1402a and the linking group 1402 b or between the linking group 1402 b andthe terminal group 1402 c—the exposed part of the masking layer 1402 canbe functionalized to produce desired characteristic(s).)

There are many particular ways in which the above-described generalapproaches to modifying a masking layer can be implemented. Theparticular implementation can depend on the particular structure and/ormaterials of the head group 1402 a, linking group 1402 b and/or terminalgroup 1402 c of the masking layer 1402, and/or on the bond(s) formedthere between. Those skilled in the art can appreciate how such generalapproaches may be particularly implemented using, for example,appropriate chemical or electrochemical processing, in view of theparticular structure and/or materials of the head group 1402 a, linkinggroup 1402 b and/or terminal group 1402 c of the masking layer 1402,and/or the bond(s) formed there between, together with the descriptiongiven above.

For example, it may be desired that the masking layer inhibit formationthereon of material used to form the capping layer and promote adhesionto material used to form a dielectric barrier layer. This can beaccomplished by establishing the terminal group of a molecule used toform a molecularly self-assembled masking layer (e.g., a SAM)—i.e.,specifying the molecule to include a particular terminal group, cleavingthe terminal group of the molecule and/or functionalizing the terminalgroup—to inhibit formation of material used to form the capping layerand promote adhesion to material used to form a dielectric barrierlayer, or by establishing the terminal group of a molecule used to forma molecularly self-assembled masking layer to inhibit formation ofmaterial used to form the capping layer, then modifying (i.e., cleavingand/or functionalizing) the terminal group to promote adhesion tomaterial used to form a dielectric barrier layer. As discussed above,silane-based SAMs can be tailored to promote or inhibit the formation ofparticular material thereon, which can be useful in facilitatingselective formation of a capping layer and/or promoting adhesion of adielectric barrier layer formed on a masking layer. The properties ofthe exposed surface of a silane-based SAM can be controlled through useof appropriately substituted silane precursors. For example, a SAMformed from reaction of octadecyltrichlorosilane is expected to producean exposed surface free of reactive functionality (i.e., saturatedhydrocarbyl only). By contrast, a SAM formed from reaction ofaminopropyltrimethoxysilane is expected to produce an exposed surfacefeaturing a high density of amine functionality. The hydrocarbyl surfacewould be expected to provide a poor surface for nucleation of materialformed using an electroless deposition process, while theamine-functionalized surface would be expected to promote suchnucleation. More generally, silane precursors with alkyl, aryl,fluoroalkyl or fluoroaryl substituents can be used to produce an exposedsurface free of reactive functionality (inhospitable for nucleation ofmaterial formed using an electroless deposition process), while exposedSAM surfaces containing reactive functionality such as hydroxyl, aminoor carboxy groups (hospitable for nucleation of material formed using anelectroless deposition process) can be produced through the use ofappropriately substituted silane precursors, as can be appreciated bythose skilled in the art. Thus, the exposed surface properties of asilane-based SAM can be controlled to inhibit formation of capping layermaterial on the SAM.

The characteristics of a masking layer can also be established (i.e.,appropriate material(s) and/or process(es) used) to produce desireddiffusion barrier properties. In particular, the characteristics of themasking layer can be established so that the masking layer provides agood barrier to diffusion of the capping layer material and/ormaterial(s) used in the formation of the capping layer (e.g., precursormaterial(s)). Establishing the characteristics of the masking layer toinhibit diffusion can be increasingly advantageous as the porosity ofdielectric material(s) used in an application of the inventionincreases. For example, it is anticipated that the invention willsometimes be implemented using a cobalt alloy (e.g., acobalt-tungsten-phosphorous alloy) to form the capping layer. In thatcase, the characteristics of the masking layer can be established sothat the masking layer provides a good barrier to diffusion of cobaltalloys and/or alloy precursors.

As discussed above (and as illustrated by FIGS. 4A and 4B, 5A and 5B, 6Aand 6B, 7A and 7B, 8A and 8B, 9A and 9B, 10A and 10B, 11A and 11B, 12Aand 12B, and 13A and 13B), the invention can be implemented so that amasking layer is formed non-selectively on both the dielectric regionand electrically conductive regions, followed by removal of all maskinglayer material formed on the electrically conductive regions, leavingthe masking layer formed only on the dielectric region. Any of a varietyof appropriate processes can be used to remove masking layer materialfrom electrically conductive regions, as known to those skilled in theart: the particular process used in an embodiment of the invention toremove masking layer material from electrically conductive regions candepend, in particular, on the characteristics of the masking layermaterial and the material used to form the electrically conductiveregions. Removal of masking layer material formed on an electricallyconductive region can be accomplished by, for example, use of a rinsingprocess to remove physi-absorbed masking layer material or by use of anetching process to remove a small part of the electrically conductiveregion at the top of the electrically conductive regions (and, thus,masking layer material formed thereon). Such process(es) may already beperformed as part of the manufacture of the electronic device to removeother contaminants from the surfaces of the electrically conductiveregions and the invention can advantageously make use of that processingto enhance the efficiency with which a masking layer is produced inimplementations of the invention in which the masking layer is initiallyformed non-selectively.

As indicated above, in steps 303 through 306 of the method 300, afterformation of the masking layer, a capping layer is formed on theelectronic device so that the capping layer is formed on theelectrically conductive regions, but not on or in the masking layerand/or the dielectric region. (Formation of a capping layer on anelectrically conductive region encompasses negligible failure of thecapping layer material to cover the electrically conductive region,i.e., capping layer material coverage failure that does not impairperformance of a method according to the invention or the functionalityof an electronic device in the production of which a method according tothe invention is used.

Additionally, no formation of a capping layer on or in the masking layerand/or dielectric region encompasses negligible formation of cappinglayer material on or in the masking layer and/or dielectric region,i.e., capping layer material formation that does not impair performanceof a method according to the invention or the functionality of anelectronic device in the production of which a method according to theinvention is used. In particular, negligible formation of capping layermaterial on or in the masking layer and/or dielectric region does notproduce unacceptable current leakage between electrically conductiveregions even if an electrically conductive material is used to form thecapping layer. Unacceptable current leakage can mean current leakagethat is worse than the current leakage between electrically conductiveregions that occurs in an electronic device in which a dielectricbarrier layer is formed over the electrically conductive regions anddielectric region, but no capping layer is formed over the electricallyconductive regions.) As indicated by step 303, the capping layer can beformed selectively on the electrically conductive regions or the cappinglayer can be formed non-selectively on both the masking layer and theelectrically conductive regions. (Selective formation of a capping layeron electrically conductive regions encompasses negligible formation ofcapping layer material on or in the masking layer and/or dielectricregion, i.e., capping layer material coverage that does not impairperformance of a method according to the invention or the functionalityof an electronic device in the production of which a method according tothe invention is used. Non-selective formation of a capping layer onboth the masking layer and the electrically conductive regionsencompasses formation of the capping layer with no preference for theelectrically conductive regions or masking layer, with some degree ofpreference for the masking layer, or with preference for theelectrically conductive regions that is inadequate to result in theformation of no or negligible capping layer material on or in themasking layer and/or dielectric region, i.e., in the last case, withpreference that is inadequate to constitute selective formation of thecapping layer on the electrically conductive regions.) When the cappinglayer is formed non-selectively on both the masking layer and theelectrically conductive regions, all capping layer material formed onthe masking layer is subsequently removed, as indicated by steps 304 and305. (Removal of all capping layer material formed on the masking layerencompasses leaving negligible capping layer material formed on themasking layer, i.e., capping layer material coverage that does notimpair performance of a method according to the invention or thefunctionality of an electronic device in the production of which amethod according to the invention is used.) Each of FIGS. 4C, 5C, 6C and7C illustrate selective formation of a capping layer 440 on theelectrically conductive regions 410, while each of FIGS. 8C and 8D, 9Cand 9D, 10C and 10D, 11C and 11D, 12C and 12D, and 13C and 13Dillustrate non-selective formation of a capping layer 440 on both themasking layer 450 and the electrically conductive regions 410, followedby removal of all capping layer material formed on the masking layer450, leaving the capping layer 440 formed only on the electricallyregions 410.

In general, the capping layer can be formed using any material(s) andprocess(es) that produce a capping layer that achieves necessary ordesirable functions of the capping layer, e.g., that inhibitselectromigration in electrically conductive regions on which the cappinglayer is formed, that inhibits diffusion of material from electricallyconductive regions on which the capping layer is formed. The material(s)and process(es) used can—and typically will—depend on whether thecapping layer is to be formed selectively or not. The capping layer canbe formed of an electrically conductive, semiconductor or electricallyinsulative (effectively non-conductive) material. (The use of asemiconductor or electrically insulative material can reduce oreliminate concern with formation of capping layer material on themasking layer that may otherwise produce unacceptable current leakagebetween the electrically conductive regions.) For example, materials(e.g., cobalt alloys, such as an alloy of cobalt, tungsten andphosphorous or an alloy of cobalt and boron; nickel alloys, such as analloy of nickel, molybdenum and phosphorous; or tungsten) and processes(e.g., electroless deposition, chemical vapor deposition) that havepreviously been used to selectively deposit a capping layer onelectrically conductive regions of a semiconductor device can be used;the presence of the masking layer on the dielectric region duringformation of the capping layer, in accordance with the invention,inhibits formation of capping layer material on the dielectric regionthat may otherwise occur as a result of inadequate selectivity of thosematerials and processes, as discussed above. Other materials andprocesses can also be used: for example, the capping layer can be formedusing tantalum or tantalum nitride, and the capping layer can be formedusing other deposition processes, such as physical vapor deposition(sputtering) or atomic layer deposition. Like the masking layer, thecapping layer can be functionalized in a desired manner (e.g., toproduce desired adhesion properties of the capping layer with respect toa material to subsequently be formed thereon, such as a dielectricbarrier layer).

The characteristics of a capping layer formed in an embodiment of theinvention can be established to produce desired properties of thecapping layer. The particular manner in which the characteristics of acapping layer are tailored (in turn, the material(s) and/or process(es)used to form the capping layer) can—and, it is anticipated, typicallywill—depend on the particular application of the invention, i.e., thecharacteristics and properties of the masking layer, electricallyconductive regions, and/or subsequently formed material (e.g.,dielectric barrier layer) of the electronic device in which the cappinglayer is to be formed. In particular, it can be desirable to establishthe characteristics of the capping layer (i.e., use appropriatematerial(s) and/or process(es)) to facilitate strong adhesion to, andselective formation on, the electrically conductive regions, e.g., sothat the capping layer nucleates better on the electrically conductiveregions than on the masking layer. The above-described materials andprocesses for depositing an electrically conductive material produce acapping layer that nucleates better on the metallic materials (e.g.,copper, aluminum) of which the electrically conductive regions aretypically made than on the materials of which the masking layer istypically made, thus making them desirable for use in many applicationsof the invention.

The presence of the masking layer prevents formation of capping layermaterial on or in (through diffusion) the dielectric region, thusenforcing good selectivity of the capping layer material for theelectrically conductive regions vis-a-vis the dielectric regionregardless of the selectivity otherwise associated with the material(s)and process(es) used to form the capping layer. In this vein, thepresence of the masking layer prevents residual electrically conductivematerial that may be left on the dielectric region after a planarizationprocess (e.g., chemical mechanical polishing) from promoting undesirednucleation of capping layer material on the dielectric region, and alsofacilitates the use of porous dielectric materials that may otherwise beunacceptably susceptible to diffusion of capping layer material. Thus,the invention provides increased flexibility in the materials andprocesses that can be used to form the capping layer, since theabove-described concerns that must be accommodated if no masking layeris present are alleviated. For example, as discussed above, theinvention enables use of materials and processes for depositing anelectrically conductive material to form a capping layer that havepreviously been inadequate to form a capping layer without producingunacceptable current leakage between electrically conductive regions,but that are effective in inhibiting electromigration because of goodadhesion to electrically conductive regions.

Additionally, since the presence of the masking layer enables productionof a capping layer by forming additional material on an electricallyregion, there is no need to create a capping layer by chemicallymodifying a top part of the electrically conductive region. Thus, theundesirable increase in resistance in the electrically conductive regionthat is associated with creation of a capping layer in that manner isavoided.

As indicated above, when the capping layer is formed non-selectively onboth the masking layer and the electrically conductive regions, allcapping layer material formed on the masking layer is subsequentlyremoved, as indicated by steps 304 and 305, so that no (or negligible)capping layer material is present over the dielectric region, thuseliminating the possibility of current leakage between the electricallyconductive regions when an electrically conductive material is used toform the capping layer. (In accordance with the usage herein ofselective formation of a capping layer, as explained above, it is notnecessary to remove capping layer material from the masking layer whenthe capping layer is selectively formed on the electrically conductiveregions; however, even in that case, as a practical matter it may bedesirable to implement the invention to remove capping layer materialfrom the masking layer to ensure that potentially detrimental cappinglayer material is not formed on the masking layer.) This can be done byremoving just the capping layer material from the masking layer (step305), or by removing some (e.g., a top part on which the capping layermaterial is formed) or all of the masking layer together with thecapping layer material formed thereon (step 304). FIGS. 10D, 11D, 12Dand 13D illustrate removal of just capping layer material from themasking layer, while FIGS. 8D and 9D illustrate removal of all of themasking layer and the capping layer material formed thereon.

In general, any appropriate process(es) can be used to remove cappinglayer material from over the dielectric region. Typically, the removalprocess(es) include process step(s) that detach the capping layermaterial, or some or all of the masking layer together with the cappinglayer material, followed by rinsing steps that remove the detachedmaterial from the electronic device. The process(es) used can—andtypically will—depend on whether only capping layer material is to beremoved, some of the masking layer is to be removed together with thecapping layer, or all of the masking layer is to be removed togetherwith the capping layer. Additionally, process(es) used can depend on thecharacteristics and properties of the capping layer material, themasking layer and (particularly if all of the masking layer is to beremoved) the material used to form the dielectric region. For example, amasking layer can be formed (or functionalized) so that a top part ofthe masking layer can be cleaved from the rest of the masking layer whensubjected to appropriate processing, as described further below. Or, amolecularly self-assembled masking layer can be formed so that theorganic backbone of the molecularly self-assembled masking layer can bebroken down and removed when subjected to appropriate processing.

FIG. 15A is a cross-sectional view of a structure 1500 including adielectric region 1501 on which is formed a masking layer 1502, acapping layer 1503 being formed, in turn, on the masking layer 1502. Themasking layer 1502 is a self-assembled monolayer (SAM). The SAMincludes: 1) a head group 1502 a formed on the dielectric region 1501,2) a linking group 1502 b connected to the head group 1502 a, and 3) aterminal group 1502 c, connected to the linking group 1502 b, on whichmaterial can subsequently be formed. FIGS. 15B through 15E arecross-sectional views of the structure 1500 after further processing toremove the capping layer 1503. Each of FIGS. 15B through 15E illustratesa different general type of approach that can be used to effect removalof a capping layer from over a dielectric region. In FIG. 15B, theentire masking layer 1502 is removed from the dielectric region 1501: asa consequence of removing the masking layer 1502, the capping layer 1503is also removed from over the dielectric region 1501. In FIG. 15C, thehead group 1502 a of the masking layer 1502 is cleaved, removing part ofthe head group 1502 a, all of the linking group 1502 b and all of theterminal group 1502 c of the masking layer 1502, together with thecapping layer 1503 formed on the masking layer 1502 (the part of thehead group 1502 a remaining on the dielectric region 1501 is designatedas H= in FIG. 15C to indicate difference from the unmodified head group1502 a of FIG. 15A). In FIG. 15D, the linking group 1502 b of themasking layer 1502 is cleaved, removing part of the linking group 1502 band all of the terminal group 1502 c of the masking layer 1502, togetherwith the capping layer 1503 formed on the masking layer 1502 (the partof the linking group 1502 b remaining on the dielectric region 1501 isdesignated as L= in FIG. 15D to indicate difference from the unmodifiedlinking group 1502 b of FIG. 15A). In FIG. 15E, the terminal group 1502c of the masking layer 1502 is cleaved, removing part of the terminalgroup 1502 c of the masking layer 1502, together with the capping layer1503 formed on the masking layer 1502 (the part of the terminal group1502 c remaining on the dielectric region 1501 is designated as T= inFIG. 15E to indicate difference from the unmodified terminal group 1502c of FIG. 15A).

There are other general types of approaches, not illustrated in FIGS.15B through 15E, that can be used to effect removal of a capping layerfrom over a dielectric region. For example, in the structure 1500, thebond between the head group 1502 a and the linking group 1502 b could bebroken, resulting in the removal of the linking group 1502 b and theterminal group 1502 c of the masking layer 1502, together with thecapping layer 1503 formed on the masking layer 1502. Or, the bondbetween the linking group 1502 b and the terminal group 1502 c could bebroken, resulting in the removal of the terminal group 1502 c of themasking layer 1502, together with the capping layer 1503 formed on themasking layer 1502. Or, the capping layer 1503 may be removed from themasking layer 1502 without affecting the structure of the masking layer1502, i.e., so that the terminal group 1502 c, the linking group 1502 band the head group 1502 a are not cleaved and the bonds there betweenare not broken. Finally, two or more of the above-described generalapproaches can be combined; this may be desirable to increase thelikelihood that the capping layer 1502 is adequately removed from overthe dielectric region 1501. Additionally, in any of the general types ofapproaches described above in which at least part of the masking layer1502 remains on the dielectric region 1501 after removal of the cappinglayer 1503, the exposed part of the masking layer 1502 can befunctionalized to produce desired characteristic(s) (this is true forany type of masking layer in accordance with the invention, not only themasking layer 1502).

There are many particular ways in which the above-described generalapproaches to effecting removal of a capping layer from over adielectric region can be implemented. The particular implementation candepend on the particular structure and/or materials of the head group1502 a, linking group 1502 b and/or terminal group 1502 c of the maskinglayer 1502, the structure and/or materials of the capping layer 1503,and/or on the bond(s) formed there between. Those skilled in the art canappreciate how such general approaches may be particularly implementedusing, for example, appropriate chemical or electrochemical processing,in view of the particular structure and/or materials of the head group1502 a, linking group 1502 b and/or terminal group 1502 c of the maskinglayer 1502, the structure and/or materials of the capping layer 1503,and/or the bond(s) formed there between, together with the descriptiongiven above.

If the capping layer is formed selectively on the electricallyconductive regions in step 303 or if, when the capping layer is formednon-selectively on the electrically conductive regions in step 303, onlycapping layer material is removed from the masking layer in steps 304and 305, the method 300 further provides in step 306 for the possibilityof subsequently removing all of the masking layer or modifying (i.e.,removing some and/or functionalizing) the masking layer. Removing allof, or modifying, the masking layer may be necessary or desirable toproduce a surface (i.e., an exposed surface of the masking layer or thedielectric region) having desired characteristics (e.g., good propensityfor adhesion to a dielectric barrier layer subsequently to be formed onthe masking layer). In the latter case (i.e., first removing the cappinglayer, then removing or modifying the masking layer), it may benecessary or desirable to remove some or all of the masking layer(and/or to functionalize the masking layer) after removing the cappinglayer (rather than together with removal of the capping layer) for oneor more of a variety of reasons: in particular, it may be easier, morelikely or only possible to produce a surface having desiredcharacteristics by first removing the capping layer, then performingfurther processing to remove or modify the masking layer. FIGS. 10E and11E illustrate removal of all of a masking layer from a dielectricregion after capping layer material has been removed from the maskinglayer. FIGS. 14B through 14D illustrate removal of some of a maskinglayer and/or functionalization of the masking layer where the maskinglayer is a self-assembled monolayer (such removal or functionalizationcan also be performed for other types of masking layer).

Any of a variety of appropriate processes can be used to remove maskinglayer material from the dielectric region, as known to those skilled inthe art. Similarly, any of a variety of appropriate processes can beused to functionalize a masking layer, as known to those skilled in theart. For example, removal of all of a masking layer formed on adielectric region can be accomplished using a process or processessimilar to those used to remove masking layer material from electricallyconductive regions, as discussed above, e.g., rinsing process(es) and/oretching process(es). Likewise, removal of part of a masking layer formedon a dielectric region can be accomplished using a process or processesas described above for removal of part of a masking layer formed on adielectric region prior to forming a capping layer. Or, removal of someor all of a masking layer after removal of the capping layer from themasking layer can be accomplished using a process or processes that arethe same as, or similar to, process(es) used to remove some or all of amasking layer together with a capping layer formed thereon (however, thepresence of the capping layer may make necessary or desirable the use ofdifferent process(es)). The particular process or processes used in anembodiment of the invention to remove masking layer material from thedielectric region and/or to functionalize the masking layer can depend,in particular, on the characteristics of the masking layer material, andmay also depend on the material used to form the dielectric region.

As indicated above, in step 307 of the method 300, a dielectric barrierlayer can be formed on the electronic device or not, depending on theproperties of the capping layer. Each of FIGS. 4E, 6D, 8E, 10F and 12Eillustrate formation of a dielectric barrier layer 430 on the electronicdevice, while each of FIGS. 5D, 7C, 9D, 11E and 13D illustrate noformation of a dielectric barrier layer on the electronic device.

If a dielectric barrier layer is formed on the electronic device, suchformation can be accomplished using any conventional material(s) andprocess(es), or in any other appropriate manner, as known to thoseskilled in the art. For example, a dielectric barrier layer can beproduced by using chemical vapor deposition to deposit silicon nitrideor silicon carbide (e.g., a Barrier Low-K Dielectric) on the electronicdevice.

As discussed above, a dielectric barrier layer has been formed onelectrically conductive material (e.g., copper) of an electronic deviceto inhibit diffusion of the electrically conductive material intoadjacent material (e.g., dielectric material subsequently formed overthe electrically conductive material) of the electronic device. However,if a capping layer can be formed of a material that provides goodinhibition of such diffusion, while still providing other requiredproperties of the capping layer (such as good adhesion to electricallyconductive regions to inhibit electromigration, and good selectivity forelectrically conductive regions so that, when the capping layer materialis electrically conductive, stray capping layer material will notproduce unacceptable current leakage between electrically conductiveregions), it may be possible to eliminate the dielectric barrier layerfrom the electronic device or, at least, reduce the thickness of thedielectric barrier layer. In some embodiments of the invention, acapping layer is formed so that diffusion of material from theelectrically conductive regions into adjacent regions is inhibited withsufficient effectiveness that the dielectric barrier layer can be formedwith a smaller thickness than would be the case if the capping layer wasnot present. In other embodiments of the invention, a capping layer isformed so that diffusion of material from the electrically conductiveregions into adjacent regions is inhibited with sufficient effectivenessthat a dielectric barrier layer need not be formed. In either case,inhibiting diffusion of material from the electrically conductiveregions into adjacent regions with sufficient effectiveness can meanthat such diffusion is inhibited (together with inhibition of suchdiffusion by a reduced-thickness dielectric barrier layer, if present)as well as, or better than, such diffusion would be inhibited by adielectric barrier layer without the presence of the capping layer. Forexample, materials described above for use in forming a capping layer inaccordance with invention, such as cobalt alloys, nickel alloys,tungsten, tantalum and tantalum nitride, can be formed in accordancewith process(es) that enable the stoichiometry, thickness and density ofthe capping layer to be controlled to produce a capping layer thatinhibits diffusion of material from the electrically conductive regionsinto adjacent regions with sufficient effectiveness that the dielectricbarrier can be eliminated or reduced in thickness. Eliminating thedielectric barrier layer or reducing the thickness of the dielectricbarrier layer reduces capacitance, which can decrease the powerconsumption and/or increase speed of operation of the electronic device.By using a masking layer on the dielectric region to minimize oreliminate selectivity as an important consideration in choosingmaterial(s) and/or process(es) for forming the capping layer, theinvention opens up new possibilities for those material(s) and/orprocess(es) that can enable formation of a capping layer that provides,in addition to adequate inhibition of electromigration, a good barrierto diffusion of electrically conductive material that can enableelimination or reduction in thickness of a conventional dielectricbarrier layer, with attendant benefits.

FIG. 3 illustrates a method, according to an embodiment of theinvention, for producing a capping layer that includes various optionalsteps. FIGS. 4A through 4E, 5A through 5D, 6A through 6D, 7A through 7C,8A through 8E, 9A through 9D, 10A through 10F, 11A through 11E, 12Athrough 12E, and 13A through 13D each illustrate the production, inaccordance with various embodiments of the invention, of a cappinglayer. A capping layer in accordance with each of the embodiments of theinvention illustrated by FIGS. 4A through 4E, 5A through 5D, 6A through6D, 7A through 7C, 8A through 8E, 9A through 9D, 10A through 10F, 11Athrough 11E, 12A through 12E, and 13A through 13D is produced using themethod 300 as follows. In the embodiment of the invention illustrated inFIGS. 4A through 4E, a masking layer 450 is formed non-selectively onboth the dielectric region 420 and the electrically conductive regions410 in the step 301 of the method 300 (FIG. 4A), all masking layermaterial is removed from the electrically conductive regions 410 in thestep 302 of the method 300 (FIG. 4B), capping layer material is formedselectively on the electrically conductive regions 410 in the step 303of the method 300 (FIG. 4C), all masking layer material is removed fromthe dielectric region 420 in the step 306 of the method 300 (FIG. 4D),and a dielectric barrier layer 430 is formed over the capping layer 440and dielectric region 420 in the step 307 of the method 300 (FIG. 4E).In the embodiment of the invention illustrated in FIGS. 5A through 5D,each of the structures illustrated in FIGS. 5A through 5D are formed asdescribed above for the structures illustrated in FIGS. 4A through 4D,respectively; unlike the embodiment of the invention illustrated inFIGS. 4A through 4E, in the embodiment of the invention illustrated inFIGS. 5A through 5D, the capping layer 440 is formed so that nodielectric barrier layer need be formed in the step 307 of the method300. In the embodiment of the invention illustrated in FIGS. 6A through6D, each of the structures illustrated in FIGS. 6A through 6C are formedas described above for the structures illustrated in FIGS. 4A through4C, respectively; unlike the embodiment of the invention illustrated inFIGS. 4A through 4E, in the embodiment of the invention illustrated inFIGS. 6A through 6D, the masking layer material is not removed from thedielectric region 420 in the step 306 of the method 300 before forming adielectric barrier layer 430 in the step 307 of the method 300 (FIG.6D). In the embodiment of the invention illustrated in FIGS. 7A through7C, each of the structures illustrated in FIGS. 7A through 7C are formedas described above for the structures illustrated in FIGS. 6A through6C, respectively; unlike the embodiment of the invention illustrated inFIGS. 6A through 6D, in the embodiment of the invention illustrated inFIGS. 7A through 7C, the capping layer 440 is formed so that nodielectric barrier layer need be formed in the step 307 of the method300. In the embodiment of the invention illustrated in FIGS. 8A through8E, a masking layer 450 is formed non-selectively on both the dielectricregion 420 and the electrically conductive regions 410 in the step 301of the method 300 (FIG. 8A), all masking layer material is removed fromthe electrically conductive regions 410 in the step 302 of the method300 (FIG. 8B), capping layer material is formed non-selectively on boththe dielectric region 420 and the electrically conductive regions 410 inthe step 303 of the method 300 (FIG. 8C), all masking layer material(and all capping layer material formed thereon) is removed from thedielectric region 420 in the step 304 of the method 300 (FIG. 8D), and adielectric barrier layer 430 is formed over the capping layer 440 anddielectric region 420 in the step 307 of the method 300 (FIG. 8E). Inthe embodiment of the invention illustrated in FIGS. 9A through 9D, eachof the structures illustrated in FIGS. 9A through 9D are formed asdescribed above for the structures illustrated in FIGS. 8A through 8D,respectively; unlike the embodiment of the invention illustrated inFIGS. 8A through 8E, in the embodiment of the invention illustrated inFIGS. 9A through 9D, the capping layer 440 is formed so that nodielectric barrier layer need be formed in the step 307 of the method300. In the embodiment of the invention illustrated in FIGS. 10A through10F, each of the structures illustrated in FIGS. 10A through 10C areformed as described above for the structures illustrated in FIGS. 8Athrough 8C, respectively; unlike the embodiment of the inventionillustrated in FIGS. 8A through 8E, in the embodiment of the inventionillustrated in FIGS. 10A through 10F, masking layer material is notremoved from the dielectric region 420 in the step 304 of the method300, though all of the capping layer material is removed in the step 305of the method 300 (FIG. 10D), after which all of the masking layermaterial is removed from the dielectric region 420 in the step 306 ofthe method 300 (FIG. 10E) followed by formation of a dielectric barrierlayer 430 on the capping layer 440 and dielectric region 420 in the step307 of the method 300 (FIG. 10F). In the embodiment of the inventionillustrated in FIGS. 11A through 11E, each of the structures illustratedin FIGS. 11A through 11E are formed as described above for thestructures illustrated in FIGS. 10A through 10E, respectively; unlikethe embodiment of the invention illustrated in FIGS. 10A through 10F, inthe embodiment of the invention illustrated in FIGS. 11A through 11E,the capping layer 440 is formed so that no dielectric barrier layer needbe formed in the step 307 of the method 300. In the embodiment of theinvention illustrated in FIGS. 12A through 12E, each of the structuresillustrated in FIGS. 12A through 12D are formed as described above forthe structures illustrated in FIGS. 10A through 10D, respectively;unlike the embodiment of the invention illustrated in FIGS. 10A through10F, in the embodiment of the invention illustrated in FIGS. 12A through12E, masking layer material is not removed from the dielectric region420 in the step 306 of the method 300 before forming a dielectricbarrier layer 430 in the step 307 of the method 300 (FIG. 12E). In theembodiment of the invention illustrated in FIGS. 13A through 13D, eachof the structures illustrated in FIGS. 13A through 13D are formed asdescribed above for the structures illustrated in FIGS. 12A through 12E,respectively; unlike the embodiment of the invention illustrated inFIGS. 12A through 12E, in the embodiment of the invention illustrated inFIGS. 13A through 13D, the capping layer 440 is formed so that nodielectric barrier layer need be formed in the step 307 of the method300.

Various embodiments of the invention have been described. Thedescriptions are intended to be illustrative, not limiting. Thus, itwill be apparent to one skilled in the art that certain modificationsmay be made to the invention as described herein without departing fromthe scope of the claims set out below.

1. A method for producing a capping layer on electrically conductiveregions of an electronic device that are separated by a dielectricregion of the electronic device, the method comprising the steps of:forming a masking layer on the dielectric region but, not on theelectrically conductive regions; and after formation of the maskinglayer, forming a capping layer on at least the electrically conductiveregions.
 2. A method as in claim 1, wherein the step of forming amasking layer comprises the step of selectively forming masking layermaterial on the dielectric region.
 3. A method as in claim 2, whereinthe step of selectively forming masking layer material comprises thestep of selectively forming a molecularly self-assembled layer on thedielectric region.
 4. A method as in claim 1, wherein the step offorming a masking layer comprises the steps of: forming masking layermaterial on the dielectric region and the electrically conductiveregions; and removing masking layer material from the electricallyconductive regions so that no or negligible masking layer materialremains on the electrically conductive regions.
 5. A method as in claim4, wherein the step of forming a capping layer comprises the step ofselectively forming capping layer material on the electricallyconductive regions.
 6. A method as in claim 5, further comprising thestep of, after formation of the masking layer and the capping layer,forming a dielectric barrier layer over the electrically conductiveregions and the dielectric region.
 7. A method as in claim 6, whereinthe step of forming a capping layer comprises forming the capping layerso that the capping layer inhibits diffusion of material from theelectrically conductive regions into adjacent regions with sufficienteffectiveness that the dielectric barrier layer can be formed with asmaller thickness than would be the case if the capping layer was notpresent.
 8. A method as in claim 5, wherein the step of forming acapping layer comprises forming the capping layer so that the cappinglayer inhibits diffusion of material from the electrically conductiveregions into adjacent regions with sufficient effectiveness that adielectric barrier layer need not be formed over the electricallyconductive regions and the dielectric region.
 9. A method as in claim 5,further comprising the step of, after formation of the capping layer,removing the masking layer.
 10. A method as in claim 9, furthercomprising the step of, after formation of the masking layer and thecapping layer, forming a dielectric barrier layer over the electricallyconductive regions and the dielectric region.
 11. A method as in claim10, wherein the step of forming a capping layer comprises forming thecapping layer so that the capping layer inhibits diffusion of materialfrom the electrically conductive regions into adjacent regions withsufficient effectiveness that the dielectric barrier layer can be formedwith a smaller thickness than would be the case if the capping layer wasnot present.
 12. A method as in claim 9, wherein the step of forming acapping layer comprises forming the capping layer so that the cappinglayer inhibits diffusion of material from the electrically conductiveregions into adjacent regions with sufficient effectiveness that adielectric barrier layer need not be formed over the electricallyconductive regions and the dielectric region.
 13. A method as in claim4, wherein the step of forming masking layer material comprises the stepof forming a molecularly self-assembled layer on the dielectric regionand the electrically conductive regions.
 14. A method as in claim 1,wherein the step of forming a capping layer comprises the step ofselectively forming capping layer material on the electricallyconductive regions.
 15. A method as in claim 1, wherein the step offorming a capping layer comprises the steps of: forming capping layermaterial on the masking layer and the electrically conductive regions;and removing capping layer material formed on the masking layer so thatno or negligible capping layer material remains formed over thedielectric region between the electrically conductive regions.
 16. Amethod as in claim 15, wherein the step of removing capping layermaterial formed on the masking layer comprises the step of removing someor all of the masking layer, thereby removing capping layer materialformed on the masking layer.
 17. A method as in claim 15, wherein thestep of removing capping layer material formed on the masking layercomprises the step of removing capping layer material such that no ornegligible masking layer material is removed.
 18. A method as in claim1, further comprising the step of, after formation of the capping layer,removing the masking layer.
 19. A method as in claim 1, furthercomprising the step of, after formation of the masking layer and thecapping layer, forming a dielectric barrier layer over the electricallyconductive regions and the dielectric region.
 20. A method as in claim19, wherein the step of forming a capping layer comprises forming thecapping layer so that the capping layer inhibits diffusion of materialfrom the electrically conductive regions into adjacent regions withsufficient effectiveness that the dielectric barrier layer can be formedwith a smaller thickness than would be the case if the capping layer wasnot present.